What is a flusher in Fortnite Chapter 7 Season 4?

In Fortnite Chapter 7 Season 4, flushers are port-a-potties that act as teleporters, sending you to a nearby location or another port-a-potty. The third step of the second part of Geno's story quest requires using a flusher to block Geno from listening to The Order's message, and the best spot is the Chopped Shop POI, which has two in the immediate area.